In various multistage turbomachines used for energy conversion, such as turbines, a fluid is used to produce rotational motion. In a gas turbine, for example, a gas is compressed through successive stages in a compressor and mixed with fuel in a combustor. The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stages to produce the rotational motion. The turbine stages and compressor stages typically have stationary or non-rotary components, e.g., vane structures, that cooperate with rotatable components, e.g., rotor blades, for compressing and expanding the operational gases.
The rotor blades are typically mounted to disks that are supported for rotation on a rotor shaft. Annular arms extend from opposed portions of adjoining disks to define paired annular arms. A cooling air cavity is formed on an inner side of the paired annular arms between the disks of mutually adjacent stages, and a labyrinth seal may be provided on the inner circumferential surface of the stationary vane structures for cooperating with the annular arms to effect a gas seal between a path for the hot combustion gases and the cooling air cavity. The paired annular arms extending from opposed portions of adjoining disks define opposing end faces located in spaced relation to each other. Typically the opposing end faces may be provided with a slot for receiving a seal strip, known as a “belly band seal”, which bridges the gap between the end faces to prevent cooling air flowing through the cooling air cavity from leaking into the path for the hot combustion gases. The seal strip may be formed of multiple segments, in the circumferential direction, that are interconnected at lapped or stepped ends, as is described in U.S. Pat. No. 6,315,301, which patent is incorporated herein by reference.
When the seal strip comprises plural segments positioned adjacent to each other, in the circumferential direction, the seal strips may shift circumferentially relative to each other. Shifting may cause one end of a seal strip segment to increase the overlap with an adjacent segment, while the opposite end of the seal strip segment will move out of engagement with an adjacent segment, opening a gap for passage of gases through the seal strip. In order to prevent rotation of the seal strip segments, the segments may be provided with pins or anti-rotation blocks to cooperate with an adjacent disk surface for holding the segments stationary relative to the disk.
For example, one known anti-rotation device comprises an anti-rotation block 2 that includes extensions 4, 5 positioned in engagement with notches formed in the seal strip 6 and located within an opening 7 in the end face of an annular arm 8 of the disk. The extensions 4, 5 are welded to the seal strip 6 to maintain the anti-rotation block 2 in position on the seal strip 6, see FIG. 5. Such an anti-rotation structure may experience cracking and failures at the weld locations. In particular, failure of the weld attaching the anti-rotation block to the seal strip may result in pieces of the seal strip becoming liberated and causing damage within the turbine. Further, applying this configuration of anti-rotation structure as a field repair requires a difficult field weld to be performed, making the quality of the repair difficult to control.